1. Field of the Invention
The present invention relates to an active matrix type liquid crystal display device and a method of forming the same, and more particularly to the active matrix type liquid crystal display device in construction, and to its electrodes for controlling a liquid crystal of the active matrix type liquid crystal display device.
2. Description of the Related Art
Heretofore, liquid crystal display devices of a so-called xe2x80x9cIn-Plate Switching (i.e., IPS)xe2x80x9d type have been proposed. FIG. 12 shows a plan view of a conventional liquid crystal display device. FIG. 13 shows a cross-sectional view of the conventional liquid crystal display device, taken along the line IVxe2x80x94IV of FIG. 12.
In a conventional liquid crystal display device 100 of the above-mentioned IPS type shown in FIGS. 12 and 13, a liquid crystal layer 107 is sandwiched between a pair of transparent glass substrates, which comprise: an opposing-side glass substrate 105; and, a thin-film-transistor-side (i.e., TFT-side) glass substrate 104 oppositely disposed from the opposing-side glass substrate 105.
Formed on the TFT-side glass substrate 104 are: a lower layer wiring 101; a lower layer comb-shaped electrode 110, wherein both the lower layer wiring 101 and the lower layer comb-shaped electrode 110 are made of non-transparent metals such as Cr, Al, Mo, etc.; an interlayer insulation film 108; and, a semiconductor layer, wherein both the interlayer insulation film 108 and the semiconductor layer are formed by a plasma enhanced CVD process (hereinafter referred to as the P-CVD process). After that, a semiconductor pattern 102 is formed by a photo resist process (hereinafter referred to as the PR process). Both an upper layer wiring 103 and an upper layer comb-shaped electrode 109 are made of the same material as that of the lower layer wiring 101. After completion of a channel etching process, a transistor protection film 114 is formed. The transistor is hereinafter referred to as Tr.
On the other hand, in the side on the opposing-side glass substrate 105, as is clear from FIG. 13, a color layer 106 is applied to the opposing-side substrate 105. Then, acrylic resins are applied to the entire surface of the opposing-side glass substrate 105 to form an overcoat layer 111, which prevents any substance issued from the color layer 106 from entering and affecting the liquid crystal layer 107 in characteristic. Then, an orientation film 112 is applied to each of the opposing-side substrates 105 and the TFT-side substrate 104. The thus applied orientation film 112 is then subjected to an orientation treatment, which is followed by formation of the liquid crystal layer 107 of a liquid crystal filled in a panel gap between the TFT-side glass substrate 104 and the opposing-side glass substrate 105.
In the so-called IPS type of liquid crystal display device having the above construction, an electric field is produced between the upper layer comb-shaped electrode 109 and the lower layer comb-shaped electrode 110 to form a lateral electric field therebetween, wherein: through the thus formed lateral electric field, the liquid crystal is controlled in operation.
In the conventional IPS type liquid crystal display device having the above construction, since its electrode for producing the lateral electric field is not transparent, the display device is poor in light transmission rate. Further, in an area of the conventional display device in which area the opposing-side electrode is brought into contact with the liquid crystal layer, it is not possible to form a transparent electrode made of a transparent metal such as ITO (i.e., Indium Tin Oxide), etc., because it is necessary to prevent the lateral electric field of the liquid crystal layer from being disturbed. Since the metal electrode excellent in barrier properties can""t be used as described above, in order to prevent any substance issued from the color layer 106 from entering the liquid crystal layer 107, it is necessary to apply the overcoat layer 111 to the entire surface of the opposing-side glass substrate 105.
Further, in the conventional display device, since no conductive element for shielding the electric field (i.e., inner electric field) produced in the liquid crystal layer 107 is formed in the opposing-side glass substrate 105, it is necessary to shield such inner electric field from any external electric field by means of a suitable shield means such as: a transparent conductive film formed in a rear surface of the substrate so as to prevent the conductive film from affecting the inner electric field; a conductive polarizing plate; or, like elements. As described above, the conventional display device suffers from various disadvantages.
In view of the above, it is an object of the present invention to provide an active matrix type liquid crystal display device and a method of forming the same, wherein:
electrodes in each of an opposing-side substrate and a TFT-side substrate are made of a transparent metal to improve the display device in light transmission rate; and, the display device may operate in substantially the same manner as that of the so-called IPS type liquid crystal display device.
According to a first aspect of the present invention, there is provided an active matrix type liquid crystal display device having:
a TFT-side substrate;
an opposing-side substrate oppositely disposed from the TFT-side substrate;
a liquid crystal sandwiched between the TFT-side substrate and the opposing-side substrate;
a transparent conductive electrode formed on an opposing surface of the opposing-side substrate, wherein the opposing surface of the opposing-side substrate faces the TFT-side substrate;
a pixel electrode provided with a plurality of pixel electrode portions formed on an opposing surface of the TFT-side substrate, wherein the opposing surface of the TFT-side substrate faces the opposing-side substrate; and
an interlayer insulation film provided with a plurality of slits each aligned in position with each of the pixel electrode portions,
wherein the liquid crystal has a negative dielectric anisotropy.
According to a second aspect of the present invention, there is provided an active matrix type liquid crystal display device having:
a TFT-side substrate;
an opposing-side substrate oppositely disposed from the TFT-side substrate;
a liquid crystal sandwiched between the TFT-side substrate and the opposing-side substrate;
a transparent conductive electrode formed on an opposing surface of the opposing-side substrate, wherein the opposing surface of the opposing-side substrate faces the TFT-side substrate;
a pixel electrode provided with a plurality of pixel electrode portions formed on an opposing surface of the TFT-side substrate, wherein the opposing surface of the TFT-side substrate faces the opposing-side substrate, and the pixel electrode portions each having an electrode width are spaced apart from each other at predetermined electrode spacings; and
an interlayer insulation film provided with a plurality of slits each aligned in position with each of the pixel electrode portions,
wherein the liquid crystal has a negative dielectric anisotropy.
In the active matrix type liquid crystal display device according to the second aspect of the present invention, preferably:
xe2x80x83W less than d
where W is an electrode width of each of the pixel electrode portions; and, d is a panel gap between the opposing-side substrate and the TFT-side substrate. Further, preferably:
d less than S less than 3d
where S is each of the electrode spacings of the pixel electrode portions; and, d is the panel gap between the opposing-side substrate and the TFT-side substrate.
According to a third aspect of the present invention, there is provided an active matrix type liquid crystal display device having:
a TFT-side substrate;
an opposing-side substrate oppositely disposed from the TFT-side substrate;
a liquid crystal sandwiched between the TFT-side substrate and the opposing-side substrate;
a transparent conductive electrode formed on an opposing surface of the opposing-side substrate, wherein the opposing surface of the opposing-side substrate faces the TFT-side substrate;
an interlayer insulation film provided with a plurality of slits, the interlayer insulation film being formed on an opposing surface of the TFT-side substrate, wherein the opposing surface of the TFT-side substrate faces the opposing-side substrate; and
a pixel electrode provided with a plurality of pixel electrode portions each capable of being embedded in each of the slits of the interlayer insulation film,
wherein the liquid crystal has a negative dielectric anisotropy.
According to a fourth aspect of the present invention, there is provided a method of forming an active matrix type liquid crystal display device, having the steps of:
sandwiching a liquid crystal between a TFT-side substrate and an opposing-side substrate which is oppositely disposed from the TFT-side substrate;
forming a transparent conductive electrode on an opposing surface of the opposing-side substrate, wherein the opposing surface of the opposing-side substrate faces the TFT-side substrate; and
forming both a pixel electrode having a plurality of pixel electrode portions and an interlayer insulation film on an opposing surface of the TFT-side substrate, wherein the opposing surface of the TFT-side substrate faces the opposing-side substrate, the interlayer insulation film being provided with a plurality of stepped slits each aligned in position with each of the pixel electrode portions,
wherein the liquid crystal has a negative dielectric anisotropy.
According to a fifth aspect of the present invention, there is provided a method of forming an active matrix type liquid crystal display device, having the steps of:
sandwiching a liquid crystal between a TFT-side substrate and an opposing-side substrate which is oppositely disposed from the TFT-side substrate;
forming a transparent conductive electrode on an opposing surface of the opposing-side substrate, wherein the opposing surface of the opposing-side substrate faces the TFT-side substrate;
forming both a pixel electrode with a plurality of pixel electrode portions and an interlayer insulation film on an opposing surface of the TFT-side substrate, wherein the opposing surface of the TFT-side substrate faces the opposing-side substrate, and the pixel electrode portions each having an electrode width are spaced apart from each other at predetermined electrode spacings to form a pixel electrode slit between adjacent ones of the pixel electrode portions, and the interlayer insulation film is provided with a plurality of stepped slits each aligned in position with each of the pixel electrode portions,
wherein the liquid crystal has a negative dielectric anisotropy.
According to a sixth aspect of the present invention, there is provided a method of forming an active matrix type liquid crystal display device, having the steps of:
sandwiching a liquid crystal between a TFT-side substrate and an opposing-side substrate which is oppositely disposed from the TFT-side substrate;
forming a transparent conductive electrode on an opposing surface of the opposing-side substrate, wherein the opposing surface of the opposing-side substrate faces the TFT-side substrate; and
forming both a pixel electrode having a plurality of pixel electrode portions and an interlayer insulation film on an opposing surface of the TFT-side substrate, wherein:
the opposing surface of the TFT-side substrate faces the opposing-side substrate; the interlayer insulation film is provided with a plurality of interlayer insulation film slits; and, each of the pixel electrode portions is capable of being embedded in each of the interlayer insulation film slits,
wherein the liquid crystal has a negative dielectric anisotropy.
In the method of forming the active matrix type liquid crystal display device according to the present invention, preferably:
the pixel electrode portions are made of a transparent metal capable of permitting light to pass therethrough.
In the present invention having the above construction, it is possible for the pixel electrode portions to permit the light to pass therethrough since the electrodes formed on both the opposing-side substrate and the TFT-side substrate are made of the transparent metal, which improves the display device of the present invention in light transmission rate in comparison with the conventional display device in which non-transparent electrodes are used. Further, in the display device of the present invention having the above construction, it is possible to control the liquid crystal by using the lateral electric field.